CVS - Cellular Events Flashcards
What happens at the top of the action potential of the ventricle
The sodium channels inactivate
Potassium current flows outward
The NCX reverses
Describe the ventricular action potential upstroke
The upstroke is caused by the opening of voltage gated sodium channels
What is happening at the plateau - peak of ventricular action potential?
Voltage gated calcium channels (L type) open
Potassium channels open
What causes the repolarisation after the cardiac action potential?
The calcium channels become inactive
The voltage gated potassium channels open
What is the pacemaker potential?
This is the diastolic membrane potential before the threshold of the SAN action potential. Caused by HCN channels open and the influx of sodium ions. This is known as the funny current
What activates HCN channels?
Hyperpolarization of the membrane
More negative than -50mV
What causes the upstroke of the SAN AP?
Voltage gated calcium channels open
What causes the repolarisation of the SAN AP?
Voltage gated potassium channels open
What is automaticity?
The ability to do some thing without thought
Which part of the heart is fastest to depolarise?
The SAN
What joins cardiomyoctes?
Intercalated disks
What anchors two myocytes together?
Desmosomes
What permits the movement of ions (electrically couples the cell)
The gap junctions
How does calcium get into the cell for contraction?
Depolarisation opens L type calcium channels in T - tubule
Ca entry opens calcium induced calcium release channels in SR
How does calcium leave the cell?
Most calcium is pumped back into the SR by SERCA
Some exits across the membrane (PMCA or NCX)
